1. Related Art
Rapid Prototyping and Manufacturing (RP&M) is the name given to a field of technologies that can be used to form three-dimensional objects rapidly and automatically from three-dimensional computer data representing the objects. RP&M can be considered to include three classes of technologies: (1) Stereolithography, (2) Selective Deposition Modeling, and (3) Laminated Object Manufacturing.
The stereolithography class of technologies create three-dimensional objects based on the successive formation of layers of a fluid-like material adjacent to previously formed layers of material and the selective solidification of those layers according to cross-sectional data representing successive slices of the three-dimensional object in order to form and adhere laminae (i.e. solidified layers). One specific stereolithography technology is known simply as stereolithography and uses a liquid material that is selectively solidified by exposing it to prescribed stimulation. The liquid material is typically a photopolymer and the prescribed stimulation is typically visible or ultraviolet electromagnetic radiation. The radiation is typically produced by a laser though other sources of radiation are possible such as arc lamps, resistive lamps, and the like. Exposure may occur by scanning a beam or by controlling a flood exposure by use of a light valve that selectively transmits or reflects the radiation. Liquid-based stereolithography is disclosed in various patents, applications, and publications of which a number are briefly described in the Related Applications section hereafter.
Another stereolithography technology is known as Selective Laser Sintering (SLS). SLS is based on the selective solidification of layers of a powdered material by exposing the layers to infrared electromagnetic radiation to sinter or fuse the powder particles. SLS is described in U.S. Pat. No. 4,863,538, issued Sep. 5, 1989, to Deckard. A third technology is known as Three Dimensional Printing (3DP). 3DP is based on the selective solidification of layers of a powdered material which are solidified by the selective deposition of a binder thereon. 3DP is described in U.S. Pat. No. 5,204,055, issued Apr. 20, 1993, to Sachs.
Selective Deposition Modeling, SDM, involves the build-up of three-dimensional objects by selectively depositing solidifiable material on a lamina-by-lamina basis according to cross-sectional data representing slices of the three-dimensional object. One such technique is called Fused Deposition Modeling, FDM, and involves the extrusion of streams of heated, flowable material which solidify as they are dispensed onto the previously formed laminae of the object. FDM is described in U.S. Pat. No. 5,121,329, issued Jun. 9, 1992, to Crump. Another technique is called Ballistic Particle Manufacturing, BPM, which uses a 5-axis, ink-jet dispenser to direct particles of a material onto previously solidified layers of the object. BPM is described in PCT publication numbers WO 96-1260,7, published May 2, 1996, by Brown; WO 96-12608, published May 2, 1996, by Brown; WO 96-12609, published May 2,1996, by Menhennett; and WO 96-12610, published May 2,1996, by Menhennett. A third technique is called Multijet Modeling, MJM, and involves the selective deposition of droplets of material from multiple ink jet orifices to speed the building process. MJM is described in U.S. Pat. No. 5,943,235 filed Sep. 27, 1996 and issued Aug. 24, 1999 to Earl et al. in U.S. patent application No. 08/722,335, filed Sep. 27, 1996, by Leyden et al. now abandoned (both assigned to 3D Systems, Inc. as is the instant application).
Laminated Object Manufacturing, LOM, techniques involve the formation of three-dimensional objects by the stacking, adhering, and selective cutting of sheets of material, in a selected order, according to the cross-sectional data representing the three-dimensional object to be formed. LOM is described in U.S. Pat. Nos. 4,752,352, issued Jun. 21, 1988, to Feygin, 5,015,312, issued May 14, 1991, to Kinzie, and 5,192,559, issued Mar. 9, 1993, to Hull et al.; and in PCT Publication No. WO 95-18009, published Jul. 6, 1995, by Morita.
The techniques of the instant invention are directed primarily to liquid-based stereolithography object formation, and more particularly to layer formation when exposure techniques are employed that leave some object portions unexposed on some layers and then expose those object portions in association with a subsequent layer. A need exists in the art for improved techniques for forming coatings of material in a more accurate and/or timely manner.
2. Other Related Patents and Applications
The patents, applications, and publications mentioned above and hereafter are all incorporated by reference herein as if set forth in full. Table 1 provides a listing of patents and applications co-owned by the assignee of the instant application. A brief description of subject matter found in each patent and application is included in the table to aid the reader in finding specific types of teachings. It is not intended that the incorporation of subject matter be limited to those topics specifically indicated, but instead the incorporation is to include all subject matter found in these applications and patents. The teachings in these incorporated references can be combined with the teachings of the instant application in many ways. For example, the references directed to various data manipulation techniques may be combined with the teachings herein to derive even more useful, modified object data that can be used to more accurately and/or efficiently form objects. As another example, the various apparatus configurations disclosed in these references may be used in conjunction with the novel features of the instant invention.
TABLE 1 __________________________________________________________________________ Related Patents and Applications Patent No. Issue Date Application No. Filing Date Inventor Subject __________________________________________________________________________ 4,575,330 Hull Discloses fundamental elements of stereolithography. Mar 11, 1986 06/638,905 Aug 8, 1984 4,999,143 Hull, et at. Discloses various removable support structures applicable to Mar 12, 1991 stereolithography. 07/182,801 Apr 18, 1988 5,058,988 Spence Discloses the application of beam profiting techniques useful in Oct 22, 1991 stereolithography for determining cure depth and scanning 07/268,816 velocity, etc. Nov 8, 1988 5,059,021 Spence, et al. Discloses the utilization of drift correction techniques for Oct 22, 1991 eliminating errors in beam positioning resulting from instabilities 07/268,907 in the beam scanning system Nov 8, 1988 5,076,974 Modrek, et at Discloses techniques for post processing objects formed by Dec 31, 1991 stereolithography. In particular exposure techniques are 07/268,429 described that complete the solidification of the building Nov 8, 1988 material. Other post processing steps are also disclosed such as steps of fitting in or sanding off surface discontinuities. 5,104,592 Hull Discloses various techniques for reducing distortion, and Apr 14, 1992 particularly curt type distortion, in objects being formed by 07/339,246 stereolithography. Apr 17, 1989 5,123,734 Spence, et at. Discloses techniques for calibrating a scanning system. In Jun 23, 1992 particular techniques for mapping from rotational mirror 07/268,837 coordinates to planar target surface coordinates are disclosed Nov 8, 1988 5,133,987 Spence, et al. Discloses the use of a stationary mirror located on an optical Jul 28, 1992 path between the scanning mirrors and the target surface to 07/427,885 fold the optical path in a stereolithography system. Oct 27, 1989 5,141,680 Almquist, et al. Discloses various techniques for selectively dispensing a Aug 25, 1992 material to build up three-dimensional objects. 07/592,5599 Oct 4, 1990 5,143,663 Leyden, et al. Discloses a combined stereolithography system for building Sep 1, 1992 and cleaning objects. 07/365,444 Jun 12, 1989 5,174,931 Almquist, et al. Discloses various doctor blade configurations for use in forming Dec 29, 1992 coatings of medium adjacent to previously solidified laminae. 07/515,479 Apr 27, 1990 5,182,056 Spence, et al. Discloses the use of multiple wavelengths in the exposure of a Jan 26, 1993 stereolithographic medium. 07/429,911 Oct 27, 1989 5,182,715 Vorgitch, et al. Discloses various elements of a large stereolithographic Jan 26, 1993 system. 07/824,819 Jan 22, 1992 5,184,307 Hull, et al. Discloses a program called Slice and various techniques for Feb 2, 1993 converting three-dimensional object data into data descriptive 07/331,644 of cross-sections. Disclosed techniques include line width Mar 31, 1989 compensation techniques (erosion routines), and object sizing techniques. The application giving rise to this patent included a number of appendices that provide further details regarding stereolithography methods and systems. 5,192,469 Hull, et at. Discloses various techniques for forming three-dimensional Mar 9, 1993 object from sheet material by selectively cutting out and 07/606,802 adhering laminae. Oct 30, 1990 5,209,878 Smalley, et al. Discloses various techniques for reducing surface May 11, 1993 discontinuities between successive cross-sections resulting 07/605,979 from a layer-by-layer building technique. Disclosed techniques include use of fill layers and meniscus smoothing. Oct 30, 1990 5,234,636 Hull, et al. Discloses techniques for reducing surface discontinuities by Aug 10, 1993 coating a formed object with a material, heating the material to 07/929,463 cause it to become flowable, and allowing surface tension to smooth the coating over the object surface. Aug 13, 1992 5,238,639 Vinson, et al. Discloses a technique for minimizing curl distortion by Aug 24, 1993 balancing upward curl to downward curl. 07/939,549 Mar 31, 1992 5,256,340 Allison, et al. Discloses various build/exposure styles for forming objects Oct 26, 1993 including various techniques for reducing object distortion. 07/906,207 Disclosed techniques include: (1) building hollow, partially Jun 25, 1992 hollow, and solid objects, (2) achieving more uniform cure and depth, (3) exposing layers as a series of separated tiles or 08/766,956 bullets, (4) using alternate sequencing exposure patterns from Dec 16, 1996 layer to layer, (5) using staggered or offset vectors from layer to layer, and (6) using one or more overlapping exposure patterns per layer. 5,321,622 Snead, et al. Discloses a computer program known as CSlice which is used Jun 14, 1994 to convert three-dimensional object data into cross-sectional 07/606,191 data. Disclosed techniques include the use of various Boolean Oct 30, 1990 operations in stereolithography. 5,597,520 Smalley, et al. Discloses various exposure techniques for enhancing object Jan 28, 1997 formation accuracy. Disclosed techniques address formation of 08/233,027 high resolution objects from building materials that have a Apr 25, 1994 Minimum Solidification Depth greater than one layer thickness and and/or a Minimum Recoating Depth greater than the desired 08/428,951 object resolution. Apr 25, 1995 08/722,335 Thayer, et al. Discloses build and support styles for use in a Multi-Jet Sep 27, 1996 Modeling selective deposition modeling system. now abandoned 5,943,235 Earl, et al. Discloses data manipulation and system control techniques for Aug 24, 1999 use in a Multi-Jet Modeling selective deposition modeling 08/722,326 system. Sep 27, 1996 5,902,537 Almquist, et al. Discloses various recoating techniques for use in May 11, 1999 stereolithography. Disclosed techniques include 1) an inkjet 08/790,005 dispensing device, 2) a fling recoater, 3) a vacuum applicator, Jan 28, 1997 4) a stream recoater, 5) a counter rotating roller recoater, and 6) a technique for deriving sweep extents. 5,840,239 Partanen, et al. Discloses the application of solid-state lasers to Nov 24, 1998 stereolithography. 08/792,347 Jan 31, 1997 6,001,297 Partanen, et al. Discloses a stereolithographic technique using a pulsed Dec 14, 1999 radiation source for solidifying layers of building material and in 08/847,855 particular the ability to limit pulse firing locations to only Apr 28, 1997 selected target locations on a surface of the medium. 08/855,125 Nguyen, et al. Discloses techniques for interpolating originally supplied cross- May 13, 1997 sectional data descriptive of a three-dimensional object to produce modified data descriptive of the three-dimensional object including data descriptive of intermediate regions between the originally supplied cross-sections of data. 5,945,058 Manners, et al. Discloses techniques for identifying features of partially formed Aug 31, 1999 objects. Identifiable features include trapped volumes, effective 08/854,950 trapped volumes, and solid features of a specified size. The May 13, 1997 identified regions can be used in automatically specifying recoating parameters and or exposure parameters. 5,902,538 Kruger, et al. Discloses simplified techniques for making high-resolution May 11, 1999 objects utilizing low-resolution materials that are limited by their 08/920,428 inability to reliably form coatings of a desired thickness due to a Aug 29, 1997 Minimum Recoating Depth (MRD) limitation. Data manipulation techniques define layers as primary or secondary. Recoating techniques are described which can be used when the thickness between consecutive layers is less than a leading edge bulge phenomena. 09/061,796 Wu, et al. Discloses use of frequency converted solid state lasers in Apr 16, 1998 stereolithography. 09/154,967 Nguyen, et al. Discloses techniques for stereolithographic recoating using a Sep 17, 1998 sweeping recoating device that pause and/or slows down over laminae that are being coated over. 09/484,984 Earl, et al. Entitled "Method and Apparatus for Forming Three-Dimensional Jan 18, 2000 Objects Using Line Width Compensation with Small Feature Retention." Discloses techniques for forming objects while compensating for solidification width induced in a building material by a beam of prescribed stimulation. 09/246,504 Guertin, et al. Entitled Method and Apparatus for Stereolithographically Feb 8, 1999 Forming Three Dimensional Objects with Reduced Distortion." Discloses techniques for forming objects wherein a delay is made to occur between successive exposures of a selected region of a layer. 09/248,352 Manners, et al. Entitled "Stereolithographic Method and Apparatus for Feb 8, 1999 production of Three Dimensional Objects using Multiple Beams of different Diameters. Discloses stereolithographic portions of lamina may be formed with a larger beam and which should be formed using a smaller beam. 09/246,416 Bishop, et al. Entitled "Rapid Prototyping Apparatus With Enhanced Thermal Feb 8, 1999 and/or Vibrational Stability for Production of Three Dimensional Objects." Discloses an improved Stereolithographic apparatus structure for isolating vibration and/or extraneous heat producing components from other thermal and vibration sensitive components. 03/248,113 Chari, et al. Entitled "Stereolithographic Method and Apparatus for Feb 8, 1999 Production of Three Dimensional Objects with Enhanced Thermal Control of the Build environment." Discloses improved stereolithographic techniques for maintaining build chamber temperature at a desired level. The techniques include varying heat production based on the difference between a detected temperature and the desired temperature. 09/247,120 Everett, et al. Entitled "Stereolithographic Method and Apparatus for Feb 8, 1999 production of Three Dimensional Objects including Enhanced Control of Prescribed Stimulation Production." Discloses techniques forming objects using varying production of prescribed stimulation (e.g. UV radiation)and enhanced scanning control. Production is reduced or eliminated during non-exposure periods (e.g. recoating, z-wait, and pre-dip defray). Production is set to a desired level based on the type of exposure that is desired. Scanning speed is set based on a number of criteria. Transition between successive exposure vectors may be made with multiple intervening non-exposure vectors. The laser power is set using an AOM in combination with a temporary detection of beam power. 09/247,110 Kulkarni, et al. Entitled "Stereolithographic Method and Apparatus for Feb 8, 1999 Production of Three Dimensional Objects Including Enhanced Control of Prescribed Stimulation Production." Discloses techniques for forming objects using a simplified data preparation process. Selection of the various parameter styles needed to form an object is reduced to answering several questions from lists of possible choices. __________________________________________________________________________
The following two books are also incorporated by reference herein as if set forth in full: (1) Rapid Prototypinq and Manufacturing: Fundamentals of Stereolithography, by Paul F. Jacobs; published by the Society of Manufacturing Engineers, Dearborn Mich.; 1992; and (2) Stereolithography and other RP&M Technologies: from Rapid Prototyping to Rapid Tooling; by Paul F. Jacobs; published by the Society of Manufacturing Engineers, Dearborn Mich.; 1996.